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A&P General > Fundamentals Of Electricity > Flashcards

Fundamentals Of Electricity Flashcards

1
Q

Differences between the conventional current flow theory and electron flow?

A

Conventional = visualization of current flowing from positive to negative

Electrons in a circuit flow from negative to positive
(Electron theory)

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2
Q

What constitutes a capacitor?

A

Two conductors separated by an insulator

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3
Q

What is the basic unit of voltage?

A

Volt

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4
Q

What is the basic unit of current?

A

Amp

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5
Q

What is the basic unit of resistance?

A

Ohm

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6
Q

Which law of electricity is the most important for an aircraft mechanic to know?

A

Ohm’s law

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7
Q

What are the three elements in Ohm’s law?

A

Voltage, current, and resistance
(Volts, amps, and ohms)

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8
Q

What are five sources of electrical energy?

A

Magnetism, chemical energy, light, heat, and pressure

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9
Q

What four things affect the resistance of an electrical conductor?

A

The material,
the cross-sectional area,
the length
the temperature

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10
Q

How can you tell the resistance of a composition resistor?

A

By a series of colored bands around his neck end of the resistor

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11
Q

What three things must all electrical circuits contain?

A

A source of electrical energy,
a load to use the energy,
conductors to join the source and the load

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12
Q

What is the basic unit of capacitance?

A

The farad

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13
Q

Why should electrolytic capacitors not be used in an AC circuit?

A

They are polarized. An electrolytic capacitor will pass current of one polarity, but will block current of the opposite polarity

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14
Q

What is meant by inductance?

A

The ability to store electrical energy in electromagnetic fields

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15
Q

What is the basic unit of inductance?

A

The Henry

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16
Q

What is meant by impedance?

A

Total opposition to current flow in an AC circuit.
Combined effect of 3 things (Resistance, inductive reactance, capacitive reactance) that opposes current flow

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17
Q

How can you find the polarity of an electromagnet?

A

Hold the electromagnet in your left hand with your fingers encircling the coil in the direction of the electrons flow. Your thumb will point to the north end of the electromagnet

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18
Q

In what units is impedance measured?

A

In ohms

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19
Q

What is the basic unit of electrical power in a DC circuit?

A

The watt

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20
Q

What is meant by a kilowatt?

A

1,000 watts

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21
Q

What happens to the current in a DC circuit if the voltage is increased but the resistance remains the same?

A

The current increases

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22
Q

What are three types of DC circuits, with regard to the placement of the various circuit components?

A

Series, parallel, and series-parallel

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23
Q

How many cells are there in a 24-volt lead-acid battery.

A

12

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24
Q

What is the specific gravity of the electrolyte in a fully charged lead-acid battery?

A

Between 1.275 and 1.300

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25
Q

What is the range of temperatures of the electrolyte in a lead-acid battery that does not require that you apply a correction when measuring its specific gravity?

A

Between 70 degrees and 90 degrees Fahrenheit

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26
Q

What instrument is used to measure the specific gravity of the electrolyte in a lead-acid battery?

A

A hydrometer

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27
Q

How is a lead-acid battery compartment treated to protect it from corrosion?

A

Paint it with an asphaltic (tar base) paint or with poly-urethane enamel

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28
Q

What is used to neutralize spilled electrolyte from a lead-acid battery?

A

A solution of bicarbonate of soda and water

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29
Q

How high should the electrolyte level be in a properly serviced lead-acid battery?

A

Only up to the level of the indicator in the cell

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30
Q

What precautions should be taken in a maintenance shop where both lead-acid and nickel-cadmium batteries are serviced?

A

The two types of batteries should be kept separate, and the tools used on one type should not be used on the other

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31
Q

Why is a hydrometer not used to measure the state of charge of a nickel-cadmium battery?

A

The electrolyte of a nickel-cadmium battery does not enter into the chemical changes that occur when the battery is charged or discharged. It is specific gravity does not change appreciably

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32
Q

What is used to neutralize spilled electrolyte from a nickel-cadmium battery?

A

A solution of boric acid and water

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33
Q

What is meant by electromagnetic induction?

A

The transfer of electrical energy from one conductor to another that is not electrically connected

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34
Q

How many ohms are in a megohm?

A

One million (1,000,000)

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35
Q

What part of an amp is a milliamp?

A

One thousandth (0.001)

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36
Q

What is meant by resistance in an electrical circuit

A

The opposition of the flow of electrons

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37
Q

What is electrical current?

A

The flow of electrons in a circuit

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38
Q

To measure voltage, is a voltmeter placed in series or in parallel with the source of voltage?

A

In parallel

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39
Q

What instrument is used to measure continuity in an electrical circuit

A

An ohmmeter

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40
Q

What instrument is used to measure current flow?

A

An ammeter

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41
Q

What instrument is used to measure voltage?

A

A voltmeter

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42
Q

What is the basic equation of ohm’s law?

A

E = I x R

E = Volage
I = Current
R = Resistance

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43
Q

What is the formula for determining power?

A

P = I x E

P= Power
I = Current
E = Volts

44
Q

What are the elements of Ohm’s law?

A

Voltage (E)
Current (I)
Resistance (R)

45
Q

What is the purpose of a capacitor?

A

It stores electrical energy in electrostatic fields

46
Q

What are five sources of electrical energy?

A

Magnetism, chemical energy, light, heat, and pressure

47
Q

How can you tell the resistance of a composition resistor?

A

By a series a colored bands around one end of the resistor

48
Q

To measure current through a component, is an ammeter placed in parallel or in series with the component?

A

In series

49
Q

What four things affect the resistance of an electrical conductor?

A

The material
The cross-sectional area
The length
The temperature

50
Q

What is the formula for power in a DC circuit?

A

Power = voltage x current
(P = E x I)

51
Q

What instrument is used to measure the specific gravity of the electrolyte in a lead-acid battery?

A

A hydrometer

52
Q

How many cells are there in a 24-volt lead-acid battery?

A

12 cells

53
Q

What instrument is used to measure electrical resistance?

A

An ohmmeter

54
Q

When measuring resistance of a component with an ohmmeter, should the circuit be energized?

A

No, there should be no power on the circuit

55
Q

What formula is used to find resistance when voltage and current are known?

A

Resistance = Voltage divided by Current

56
Q

What formula is used to find current when voltage and resistance are known?

A

Current = voltage divided by resistance

I = E/R

57
Q

What two things happen when current flows through a conductor?

A

Heat is generated and magnetic field surrounds the conductor

58
Q

What is meant by true power in an AC circuit?

A

The product of the circuit voltage and the current that is in phase with this voltage

59
Q

What is the relationship between mechanical and electrical power?

A

1 hp = 746 watts

60
Q

What is meant by reactive power in an AC circuit?

A

The power consumed in the inductive and capacitive reactance in an AC circuit. (Reactive power is also called wattless power)

61
Q

What is meant by power factor in an AC circuit?

A

The ratio of true power to apparent power. It is also the ratio of circuit resistance to circuit impedance.

62
Q

What is meant by the capacity rating of a lead-a is battery?

A

The number of hours a battery can supply a given current flow

63
Q

What electrolyte is used in a lead-acid battery?

A

A mixture of sulfuric acid and water

64
Q

How many cells are there in a 24-volt lead-acid battery?

A

12 cells

65
Q

Does the specific gravity of the electrolyte in a lead-acid battery increase or decrease as the battery becomes discharged?

A

It decreases

66
Q

What is used to neutralize spilled electrolyte from a lead-acid battery?

A

A solution of bicarbonate of soda and water

67
Q

In what units is battery capacity expressed?

A

In ampere-hours

68
Q

To measure voltage, is a voltmeter placed in series or in parallel with the source of voltage?

A

In parallel

69
Q

What are the sources that produce electrical energy?

A
  • Chemical
  • Thermal
  • Pressure
  • Light
  • Magnetic
70
Q

What does an electrical circuit consists of?

A
  • Power source
  • A conductor (wires)
  • A load or resistance (bulb, heater, etc)
71
Q

What device represents capacitance in an AC circuit?

A

A capacitor

72
Q

What are the units for frequency?

A

Hertz (Hz)

73
Q

What is the name of the component that allows current to flow in only one direction?

A

A diode

74
Q

What is the inductor in a magneto?

A

The coil, like most circuits

75
Q

What is inductance?

A

The tendency of an electrical conductor, like a coil, to oppose any change of electrical current flowing through it

76
Q

What causes opposition to the flow of current in an AC circuit?

A
  • Resistance
  • Inductive reactance
  • Capacitance reactance
76
Q

What is the general purpose of a resistor?

A

To limit or regulate the flow of current

76
Q

What are two things that happen when current flows through a conductor?

A
  • The conductor generates heat
  • A magnetic field is generated
77
Q

What is the name for the lines of force that make up a field surrounding a magnet?

A

Magnetic flux

78
Q

What is the concept that describes the relationship between electricity and magnetism?

A

Electromagnetism

79
Q

When using a hydrometer to check the charge of a lead-acid battery, at what temperatures must a correction factor be applied to the reading?

A

Below 70 F or above 90 F

80
Q

What is electromagnetic induction?

A

The use of magnetic fields to produce current or the use of current to produce a magnetic field

81
Q

What gases are released when a lead-acid battery is being charged?

A

Hydrogen and oxygen

82
Q

What is the electrolyte used in a nickel-cadmium battery?

A

Potassium hydroxide and water

83
Q

Why is a hydrometer not used to measure the state of charge of a nickel-cadmium battery?

A

The electrolyte level of a nickel-cadmium battery does not enter into the chemical changes that occur when the battery is charged or discharged. Its specific gravity does not change appreciably

84
Q

Is the electrolyte level of a nickel-cadmium battery lowest when the battery is fully charged or fully discharged?

A

Fully discharged

85
Q

What is the result of cell imbalance in a nickel-cadmium battery?

A

The low internal resistance allows current to flow between the unbalanced cells and generate heat

86
Q

What is a thermal runaway?

A

The large current flow allowed by the low internal resistance causes the cells to produce more heat than they can dissipate

87
Q

How may thermal runaway be prevented?

A

By carefully monitoring the temperature of the cells and controlling the charging current to prevent an excess of current flowing into the battery

88
Q

How is it possible to know when a nickel-cadmium battery is fully charged?

A

Completely discharge the battery and give it a constant-current charge to 140% of its ampere-hour capacity

89
Q

What is used to neutralize spilled electrolyte from a nickel-cadmium battery?

A

A solution of boric acid and water

90
Q

What is a transformer, and how does it work?

A

A device that changes electrical energy in an alternating current (AC) circuit of a given voltage into electrical energy at a different voltage level. It consists of two coils that are not electrically connected but arranged so that the magnetic field surrounding one coil cuts through the other coil.

91
Q

What three things must an electric circuit contain?

A
  • A source of electrical energy
  • A load to use the energy
  • Conductors to join the source and the load
92
Q

What is the basic function of a switch?

A

Switches control the current flow in most aircraft electrical circuits

93
Q

What is a relay?

A

A relay is simply an electromechanical switch where a small where a small amount of current can control a large amount of current

94
Q

What is the function of a current limiter?

A

A current limiter is a type of heavy-duty fuse. (30 amps or greater)
They are often used to protect a section of an electrical system, such as a single electrical bus.

95
Q

What materials are fixed resistors made of?

A

Most common fixed resistors are made of a carbon composition.
Other types of fixed resistors include carbon film, metal-oxide, metal film, and metal glaze

96
Q

What are the two main types of variable resistors?

A

Rheostat and the potentiometer

97
Q

How can you tell the resistance of a composition resister?

A

By a series of colored bands around one end of the resistor

98
Q

What happens to the current in a conductor if the length of the conductor is doubled with all other parameters unchanged?

A

The resistance of the conductor would double and current flow would be decreased

99
Q

What are binary numbers?

A

The binary number system has only two digits: 0 and 1

100
Q

What type of drawing depicts electrical components with respect to each other within a circuit?

A

An electrical schematic

101
Q

What are the two general types of AC motors used in aircraft systems?

A

Induction motors and synchronous motors

102
Q

What is the formula used to determine the speed of an AC motor?

A

RPM = (120 X Frequency) / Number of poles

103
Q

In what types of applications is a series wound DC motor most often used?

A

Applications that require high torque and low speed, such as a starter motor

104
Q

What are the two principal parts of a DC motor?

A

The field assembly and an armature assembly

A&P General (4 decks)

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